In your lab notebook, write a hypothesis (& science reason) for the following:

IV DV• 1. temperature °C Solubility (solute g/100 g of water)

• 2. mass (g) of box force (N) to overcome friction• 3. mentos candy foam volume (L)• 4. acetic acid vol. (ml) carbon dioxide volume (L)• 5. Tee shirt color Temperature (°C)

Hypothesis Wording for Quantity• You make a prediction and then justify it with a science

concept.• If (your IV increases), then (your DV response to the

change).• Simply worded – not If (IV), then (IV change that will

most affect DV). • This will happen because … use the science to justify.• Science is NOT CIRCULAR REASONING.• Compare your hypothesis to the trend statement: As

(your IV) increases, the (DV)… What’s the response to the change? State what the best fit line does.

What’s the correct hypothesis wording?

• IV = temperature (°C)• DV = solubility (solute g/100 g of water)

• A. If 4 different temperatures are tested, then 50°C will have the best solubility.

• B. If the temperature increases, then the solubility of the solute (g/100 g of water) will increase.

• C. If the temperature decreases, then the solubility of the solute (g/100 g of water) will decrease.

This will happen because…

• A. …the solute and solvent are both polar molecules and, therefore, compatible.

• B. …a solid solute dissolves more easily as temperature increases.

• C. …gas solubility in a liquid solvent decreases with temperature.

What’s the correct trend wording?

A. As the temperature increased, the solubility in 100 g of water increased.

B. As the solubility in 100 g of water increased, the temperature increased.

C. As the temperature decreased, the solubility in 100 g of water decreased.

D. As the solubility in 100 g of water decreased, the temperature decreased.

Don’t forget the data to support your trend statement.

• At 0°C the solubility was 18 g of solute/100 g of water, ……, and at 100°C the solubility was 49 g of solute/100 g of water. The overall % change from 0° to 100°C was 172%.*

• (Use all the data points – I am saving time)• *[(49-18)÷18] x 100

What’s the correct trend wording?A. As the temperature increased, the solubility in

100 g of water increased.B. As the temperature increase, nothing happened

at low temperatures; then the solubility increased at higher temperatures.

C. None of the above.

What’s the correct trend wording?Same data – scale is important.

A. There is no trend.B. As the temperature increased, the solubility of

NaCl in 100 g of water did not change.

Supporting Data• At 0°C the solubility was 38 g of NaCl /100 g of

water, ……, and at 50°C the solubility was 38.5 g /100 g of water. The percent change from 0° to 50°C was only 1.3%*.

• Again, I saved time, but you need to state all the data. Use % change to really show effect (or no effect).

• *[(38.5 – 38) ÷ 38] x 100

What’s the correct hypothesis wording?

• IV = mass (g) of box• DV = force (N) to overcome friction

• A. If 4 different size boxes are tested, then smallest size will need the least amount of force.

• B. If box mass is tested, then the 20 g size will need the most force to overcome friction.

• C. If the box mass (g) increases, then the force (N) to overcome friction will increase.

This will happen because…• A. …friction depends on the surface types. Friction

increases with surface roughness.• B. …friction depends on how hard two surfaces press

together. Increasing mass of an object increases the force of an object resting on another surface.

• The science should explain the IV effect on the DV. “A” & “B” both describe the factors that affect friction but “B” explains mass affecting amount of force needed to overcome friction.

Correct Hypothesis Wording

• Compare your wording.• What did you do correct?• Is the wording simple?• What might the trend look be? Follow the

template.

IV = mentos candy (number)DV = foam volume (L)

• If the number of mint mentos candies in 2 L of Diet Coke increases, the foam volume (L) produced will increase. The candy’s pitted surface increases the surface area exposed to the soda, which chemically react to produce more carbon dioxide; the CO2 gas forcefully escapes from the soda bottle causing foam.

IV = acetic acid volume (mL) DV = carbon dioxide volume (mL)

• If the volume (mL) of acetic acid mixed with sodium bicarbonate increases, then the carbon dioxide volume (mL) will increase. Carbon dioxide gas is produced when an acid and carbonate chemically react. Increasing the reactant(s) increases the products of a chemical reaction.

• These last two slides show research to explain results. Both experiments were examples of chemical reactions – results were because new substances were produce.

What if your IV is a category?

• You need to mention ALL the IV changes that are tested. Your prediction must state which particular change has the most effect on the DV.

• You need an operational definition of what the most effect actually is.

• Don’t make an actual numerical prediction for the DV. Are you a psychic?

IV = Tee shirt color (changes to IV = white, blue, red, green, & black)DV = Temperature (°C) under the shirt

• If different colored tee shirts (white, black, red, green, and blue) are left in the sun, then the black shirt will have the highest temperature after one hour.

• If tee shirts are tested, then the black one will have the greatest effect on the temperature.

• If different colors are used, then the black one will be the best at 30°C.

The Effect of Tee Shirt Color on the Temperature (°C) Underneath the Shirt

after 1 hour Exposure to Sunlight

How do you state the trend if the Independent Variable is a category?

• We don’t state a trend since we don’t have numbers to compare within the IV.

• Simply state which IV change showed the greatest effect and which one showed the least effect on the DV.

• In our tee shirt example, the black shirt had the highest temperature at 26.6° and the white shirt had the lowest temperature at 21.5 °C.

Anyone want to guess the science to explain this one?

Temperature measures thermal energy (total energy of atoms and molecules.

↓ Sunlight is electromagnetic energy (light energy)

↓Electromagnetic energy transforms to thermal energy

↓White reflects all sunlight and black absorbs light

↓More light energy transforms to thermal energy under the

black shirt resulting in higher temperature.