9th grade science

Example

A balance shows 0.3 g when nothing is on it. What kind of error is this?

1. A scale that does not start at zero adds the same error every time: a systematic (zero) error.
2. So the answer is: a zero error (a systematic error)

Answer: a zero error (a systematic error)

Example

Which is the balanced symbol equation for photosynthesis?

1. carbon dioxide + water → glucose + oxygen (light energy, chlorophyll)
2. Left: 6 C, 12 H, 18 O. Right: 6 C, 12 H, 18 O.
3. So the answer is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Answer: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Example

Does this process remove carbon dioxide from the air or add it: decomposition by microorganisms?

1. Respiration, combustion and decomposition release carbon dioxide.
2. So the answer is: adds CO₂ to the air

Answer: adds CO₂ to the air

Example

On a chromatogram the solvent front moved 12 cm from the start line and a spot moved 0.1 cm. What is the Rf value of the spot? Give 2 decimal places.

1. 0.1 ÷ 12 = 0.008
2. So the answer is: 0.01

Answer: 0.01

Example

Where did most of the oxygen in today's atmosphere come from?

1. Algae and later plants released oxygen by photosynthesis.
2. So the answer is: photosynthesis by algae and plants over billions of years

Answer: photosynthesis by algae and plants over billions of years

Example

Today's dry air is about 78 % nitrogen and 21 % oxygen. What percentage is made up of all the other gases together?

1. 100 − 78 − 21 = 1
2. So the answer is: 1 %

Answer: 1 %